Day 8 part 2

This commit is contained in:
Wesley Moore 2022-12-09 08:41:48 +10:00
parent 83c8bbc5dd
commit 7816717cad
No known key found for this signature in database
2 changed files with 73 additions and 1 deletions

View file

@ -1,9 +1,13 @@
import gleam/io.{debug}
import gleam/int import gleam/int
import gleam/iterator.{zip} import gleam/iterator.{zip}
import gleam/string import gleam/string
import gleam/list import gleam/list
import gleam/option.{None, Some} import gleam/option.{None, Some}
type Point =
#(Int, Int)
pub fn pt_1(input: String) -> Int { pub fn pt_1(input: String) -> Int {
let trees_by_row = let trees_by_row =
input input
@ -47,7 +51,16 @@ pub fn pt_1(input: String) -> Int {
} }
pub fn pt_2(input: String) -> Int { pub fn pt_2(input: String) -> Int {
todo let trees =
input
|> string.split("\n")
|> list.map(parse_row)
trees
|> list.index_map(fn(x, row) {
list.index_map(row, fn(y, tree) { scenic_score(trees, x, y, tree) })
})
|> best_score
} }
fn parse_row(row: String) -> List(Int) { fn parse_row(row: String) -> List(Int) {
@ -113,3 +126,57 @@ fn count_if_visible(
False -> count False -> count
} }
} }
fn scenic_score(trees: List(List(Int)), x: Int, y: Int, tree: Int) {
let up = visible(trees, #(x, y), #(0, -1), tree, 0)
let down = visible(trees, #(x, y), #(0, 1), tree, 0)
let left = visible(trees, #(x, y), #(-1, 0), tree, 0)
let right = visible(trees, #(x, y), #(1, 0), tree, 0)
up * down * left * right
}
fn visible(
trees: List(List(Int)),
from: Point,
delta: Point,
tree: Int,
count: Int,
) -> Int {
let last = list.length(trees) - 1
let coord = add(from, delta)
case coord {
#(-1, _) | #(_, -1) -> count
#(x, y) if x > last || y > last -> count
#(x, y) ->
case
trees
|> list.at(x)
|> unwrap
|> list.at(y)
|> unwrap
{
other if other < tree -> visible(trees, coord, delta, tree, count + 1)
otherwise -> count + 1
}
}
}
fn best_score(scores: List(List(Int))) -> Int {
scores
|> list.map(list_max)
|> list_max
}
fn add(from: Point, delta: Point) -> Point {
#(from.0 + delta.0, from.1 + delta.1)
}
fn unwrap(x: Result(a, Nil)) -> a {
assert Ok(ok) = x
ok
}
fn list_max(l: List(Int)) -> Int {
list.reduce(l, int.max)
|> unwrap
}

View file

@ -20,3 +20,8 @@ pub fn pt1_test() {
day_8.pt_1("30373\n25512\n65332\n33549\n35390") day_8.pt_1("30373\n25512\n65332\n33549\n35390")
|> should.equal(21) |> should.equal(21)
} }
pub fn pt2_test() {
day_8.pt_2("30373\n25512\n65332\n33549\n35390")
|> should.equal(8)
}